1. Field
This disclosure relates generally to the field of wireless communication systems and more specifically to the systems and methods for a better system reselection in a multi-system wireless communication environment.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, multimedia and other. Examples of such communication systems include Code Division Multiple Access (CDMA) systems, Wideband CDMA, Global System for Mobile communications (GSM), Universal Mobile Telecommunication System (UMTS), 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, and other types of wireless communication systems. These wireless communication systems generally use different radio access technologies and communication protocols, operate at different frequency bands, provide different quality of service (QoS) and offer different types of services and applications to the system users.
Due to the differences between these systems, popularity of multimode mobile devices that are capable of operating on multiple heterogeneous wireless communication systems has grown. Multimode mobile devices are generally programmed to search for all available communication systems and connect to the most-preferred one, as specified by the operator or user preference. However, if a mobile device is acquired on a less-preferred network, the device may remain on that network for a long time. Better system reselection procedures address this problem. Generally, the system operators provision mobile devices with a list of systems ordered by preference. The mobile device can use this information to reselect to the most-preferred available system, while remaining camped on the currently acquired system.
However, known system reselection techniques have limitations. For example, if the reselection period is too large, the mobile device would spend a longer time camped on the current less-preferred system. This could be detrimental to operator requirements. On the other hand, if reselection is done too often, the device will use a significant amount of time and power in scanning for other systems, which would adversely affect the battery life. Duration of the scan may also cause problems. During reselection scan, the mobile device's radio is tuned to frequencies other than the current channel. This means the device spends time not monitoring the paging channel on the current system, which may result in missed pages. Thus, having a long scan provides a disadvantage. In contrast, if the duration is too small, and if the reselection scan list is long enough to not fit in a single reselection instance, the device may never find the better system located at the end of the scan list.